A battery unit assembly

Abstract

A battery unit assembly 100, suitable for a vehicle, comprises: a housing 102 defining a cavity 104 for enclosing a battery 106; and a hose 108 connected to the housing and in fluid communication with

Description

TECHNICAL FIELD The present disclosure relates to a battery unit assembly. Aspects of the invention relate to a battery assembly unit and a vehicle comprising the battery unit assembly. BACKGROUND It is known in battery powered vehicles to provide a battery within a sealed enclosure to prevent ingress of water or dust into the battery. In addition to the battery, such sealed enclosures contain a volume of air. During use of the vehicle, changes in the volume of air occur due to temperature changes of an ambient environment and the battery, and due to pressure changes in the ambient environment. Changes in the volume of air in the sealed enclosure can cause damage to the battery and a seal of the enclosure. Therefore, sealed enclosures for batteries are provided with water-resistant air permeable membranes. The membranes allow air to flow into and out of the enclosure. As such, pressure between the inside and the outside of the sealed enclosure may be equalised increasing the durability of the seal of the enclosure and reducing the risk of damage to the battery. The membranes also resist water entering the enclosure which may cause damage to the battery. However, such membranes are only water resistant up to a Water Entry Pressure of the membrane. The Water Entry Pressure is the minimum pressure required to force water through an opening of the membrane. If the pressure difference across the membrane is greaterthan the Water Entry Pressure of the membrane, the membrane is no longer water-tight and water may enter the sealed enclosure through the membrane. The Water Entry Pressure of certain membranes may be exceeded when the vehicle wades through water such that at least of part of the sealed enclosure of the battery and the membrane is submerged in water. This may occur when the battery is warm and the enclosure becomes submerged in cold water for a prolonged period. The battery then cools causing the pressure within the enclosure to reduce. The reduction in pressure may exceed the Water Entry Pressure of a membrane. The Water Entry Pressure varies fordifferent membranes. In general, as the air permeability of a membrane increases the Water Entry Pressure decreases. As such, membranes which remain water tight during wading may be less efficient at ventilating the sealed enclosure. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. In particular, certain embodiments of the present invention seek to improve ventilation of a battery enclosure whilst preventing water ingress during wading events. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a battery unit assembly and a vehicle as claimed in the appended claims According to an aspect of the present invention there is provided a battery unit assembly. The battery unit assembly comprising: a housing defining a cavity for enclosing a battery; and a hose connected to the housing and in fluid communication with the cavity; wherein the hose comprises an air-permeable membrane for ventilation of the cavity. The air permeable membrane in the assembly allows an exchange of air between the cavity of the housing and an ambient environment. This may reduce the risk of damage to a battery within the housing orthe housing itself due to pressure changes within the housing. Providing the air-permeable membrane for ventilation on a hose enables the membrane to be positioned away from the housing and, for example, above a wading depth of a vehicle. Therefore, a membrane with a high air permeability may be selected because the positioning of the membrane ensures that the Water Entry Pressure of the membrane is exceeded during wading as the membrane is not submerged. The risk of water ingress into the housing through the membrane is therefore reduced. In an embodiment, the air-permeable membrane may be for ventilation of the cavity in a first operating range. In an embodiment, the housing may comprise an exhaust mechanism for ventilation of the cavity in a first operating range. According to another aspect of the present invention there is provided a battery unit assembly. The battery unit assembly comprising: a housing defining a cavity for enclosing a battery; and a hose connected to the housing and in fluid communication with the cavity; wherein the hose comprises an air-permeable membrane for ventilation of the cavity in a first operating range; and wherein the housing does not comprise an air-permeable membrane for ventilation in the first operating range. The air permeable membrane in the assembly allows an exchange of air between the cavity of the housing and an ambient environment. This may reduce the risk of damage to a battery within the housing orthe housing itself due to pressure changes within the housing. Providing the air-permeable membrane for ventilation on a hose and no air-permeable membranes on the housing enables all membranes for ventilation of the cavity in a first operating range to positioned to be positioned away from the housing and, for example, above a wading depth of a vehicle thereby reducing the risk of water ingress into the housing during wading events. Additionally, in embodiments in which the membrane is not be submerged during wading, a membrane with high air permeability may be used to improve ventilation of the cavity. The assembly may be configured such that in the first operating range air exchange between the cavity and the ambient environment only occurs via the air-permeable membrane of the hose. In embodiments of either the above-described aspects of the invention, one or more of the following may apply. In an embodiment, the housing may not comprise an air-permeable membrane. That is, there is no air-permeable membrane on the housing for ventilation of the cavity in the first operating range or any other operational range. During a wading event, the housing may be submerged in water. The absence of air permeable membranes on the housing may further reduce risk of water ingress into the housing of the battery during wading events due to a Water Entry Pressure being exceeded. In an embodiment, the air-permeable membrane of the hose may be hydrophobic. As such, the risk of water from rain or spray entering the assembly through the membrane is reduced. In an embodiment, the hose may comprise a proximal end connected to the housing and a distal end. The distal end may comprise the air-permeable membrane. Placing the air-permeable membrane at the distal end of the hose may improve the ease of positioning the air-permeable membrane above the wading depth of a vehicle and enable the assembly to be used in vehicles which have large maximum wading depths. Optionally, the hose may comprise a curved portion between the distal end and the proximal end, wherein the curved portion may provide an air lock configured to restrict the flow of liquid from the distal end to the proximal end of the hose. The shape of the hose reduces the risk of liquid entering the hose via the membranes and flowing into the housing and the battery. Optionally, the battery unit assembly may comprise a protective sleeve extending around at least a portion of the hose. The sleeve may be used to protect the hose from abrasion and / or impacts thereby improving the durability of the hose. This is particularly advantageous if the hose cannot be entirely enclosed within the vehicle, for example, if the hose extends around a wheel arch in a vehicle and is not entirely covered by the wheel arch line. The protective sleeve may have a greater resistance to abrasion and / or impact than the hose. In an embodiment, the hose may comprise an end cap connected to a tube body. The end cap may comprise the air-permeable membrane. Providing the air-permeable membrane in an end cap may improve the ease and simplicity of manufacture of the battery assembly unit. This is because the connector and tube body may be formed independently and may be independent optimised for different vehicle models. Additionally, providing the air-permeable membrane at the end of the hose and on a separate component to the tube body may improve the ease of replacement of the air-permeable membrane. In an embodiment, the battery unit assembly may comprise a battery. In an embodiment, the first operating range may comprise a difference in pressure of less than 150 mbar between the cavity and the ambient environment. As such, the air-permeable membrane allows ventilation of the cavity under normal operating conditions such as temperature changes of an ambient environment and the battery and pressure changes in the ambient environment. However, in certain embodiments, the air permeable membrane may not allow for an emergency release of pressure caused by, for example, a failure or rupture of a battery cell of the battery. In an embodiment, the housing may comprise an exhaust mechanism for ventilation of the cavity in a second operating range. The exhaust mechanism may allow for emergency ventilation of the cavity caused by, for example, a failure or rupture of a battery cell of the battery. The exhaust mechanism may reduce the risk of damage to the battery due to pressure build up within the housing over a different operational range to the air-permeable membrane. The first operating range may not overlap with the second operating range. Optionally, the second operating range may comprise a difference in pressure of greater than 150 mbar between the cavity and the ambient environment. The exhaust mechanism may not comprise an air-permeable membrane for ventilating the cavity in a first operational range. The exhaust mechanism may not comprise an air-permeable membrane. As such, if the housing is submerged during a water event, there is no risk of water entering the housing due to a Water Entry Pressure of a membrane on the exhaust mechanism being exceeded. According to another aspect of the invention, there is provided a vehicle comprising a battery unit assembly according to any one of the above-described aspects of the invention, wherein the hose is positioned in the vehicle such that the air-permeable membrane is above a maximum wading depth of the vehicle. In an embodiment, the maximum wading depth may be at least 250 mm. In an embodiment, the maximum wading depth may be at least 900 mm. Optionally, the maximum wading depth may be at least 450 mm, 500 mm, 550 mm, 600 mm, 850 mm, 950 mm or 1000 mm. In an embodiment, the hose may be positioned in the vehicle such that the air-permeable membrane is at least 100 mm above a maximum wading depth of the vehicle. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a battery unit assembly within a vehicle according to an embodiment of the invention; Figure 2 shows a part of the battery unit assembly of Figure 1; Figure 3 shows a part of the battery unit assembly and the vehicle of Figure 1; Figure 4 shows a part of the battery unit assembly of Figure 1; Figures 5 and 6 each show a battery unit assembly according to another embodiment of the invention; and Figure 7 shows a part of the battery unit assembly of Figure 5. DETAILED DESCRIPTION Figure 1 shows a battery unit assembly 100 according to an embodiment to the invention. As shown in Figure 1, a vehicle 1000 may comprise the battery unit assembly 100. The battery unit assembly 100 comprises a housing 102. The housing 102 may comprise a sealed housing. That is, the housing may be sealed to prevent or reduce ingress of liquid, such as water, into the housing 102. The housing 102 defines a cavity 104 for enclosing a battery 106. The battery 106 may comprise a plurality of connected battery cells. In certain embodiments, the battery unit assembly 100 may comprise the battery 106. As shown in Figure 1, the housing 102 may be mounted to under a floor (not shown) of the vehicle 1000. As such, the housing 102 may be underneath one or both of a first row and a second row of seats (not shown). As shown in the embodiment in Figure 1, housing 102 may be positioned between a front wheel arch 1002 and a rear wheel arch 1004 of the vehicle 1000. The battery unit assembly 100 comprises a hose 108 connected to the housing 102. The hose 108 may be connected to an end of the housing 102. When the battery until assembly 100 is within the vehicle 1000, the hose 108 may be connected to an end of the housing 102 which is closest to the rear 1006 of the vehicle 1000. The hose 108 is shown in detail in Figures 2 and 3. As shown in Figures 2 to 3, the hose 108 may extend from a proximal end 110 connected to the housing 102 to a distal end 112. The hose 108 extends away from the housing 102 so that the distal end 112 of the hose 108 is spaced apart from (i.e. separated by a distance form) the housing 102. As such, when the battery unit assembly 100 is within the vehicle 1000, the distal end 112 of the hose 108 may be vertically higher than the housing 102. The hose 108 may be configured to extend vertically upwards from the housing 102 when the battery unit assembly 100 is within the vehicle 1000. The hose 108 may also be configured to extend rearwards (i.e. towards the rear 1006 of the vehicle 1000) from the housing 102 when the battery unit assembly 100 is within the vehicle 1000. As shown in Figure 2, the hose 108 may not be straight. As shown in the embodiment in Figures 1 and 3, the hose 108 may be configured such that when the battery unit assembly 100 is in the vehicle 1000, the distal end 112 of the hose 108 is above the rear wheel arch 1004. As shown in Figures 1 to 3, the hose 108 may comprise a plurality of bends 114 to facilitate arrangement of the hose 108 within the vehicle 1000. The bends 114 may enable the hose 108 to extend around components within the vehicle 1000. The hose 108 may comprise one or more straight sections 116. The one or more straight sections 116 may extend between or from the plurality of bends 114. Therefore, the hose 108 may follow a convoluted path from the proximal end 110 to the distal end 112. The number, size and shape of the plurality of bends 114 and one or more straight sections 116 may be selected depending on the vehicle 1000 in which the battery unit assembly 100 is mounted. The entirety of the hose 108 may not extend vertically upwards relative to the housing 102 when the battery unit assembly 100 is within the vehicle 1000. For example, as shown in the embodiment in Figure 3, starting at the proximal end 110, the hose 108 may first extend in a downward and rearward direction before extending in a upward and rearward direction. As shown in the embodiment in Figures 1 to 3, the hose 108 may comprise a tube body 118 extending from the proximal end 110 towards the distal end 112. The tube body 118 may comprise the plurality of bends 114. The tube body 118 may also comprise the one or more straight sections 116. The hose 108 is in fluid communication with the cavity 104. Therefore, air may flow between the cavity 104 and the hose 108. The hose 108 may comprise a connector 120 at the proximal end 110 for connecting to the housing 102. The hose 108 may comprise a tube body 118 extending away from the connector 120. The connector 120 may be configured to provide fluid communication between the cavity 104 and an internal conduit in the tube body 118. The connector 120 of the hose 108 and the housing 102 may be connected together using any suitable means. For example, the battery unit assembly 100 may comprise a spigot (not shown) configured to attach to an opening (not shown) in the housing 102. The opening in the housing 102 may extend through a wall of the housing 102 into the cavity 104. A first end of the spigot may comprise a thread to engage a corresponding thread in the opening of the housing 102. The battery unit assembly 100 may comprise a seal (not shown) arranged to provide a fluid tight seal between the first end of the spigot and the housing 102. The seal may comprise a o-ring or a gasket. A second end of the spigot may be configured to engage the connector 120 of the hose 108. The connection between the connector 120 and the spigot may be provided by any suitable means. In certain non-limiting examples, the second end of the spigot may connect to the hose 108 via a screw fit, a friction fit and a snap fit. The battery unit assembly 100 may comprise a seal (not shown) arranged to provide a fluid tight seal between the second end of the spigot and the hose 108. The seal may comprise an o-ring or a gasket. The connection between the hose 108 and the housing 102 may therefore be sealed so as to prevent water ingress into the battery unit assembly 100. The hose 108 comprises an air-permeable membrane 109 (not shown) and, optionally a plurality of air-permeable membrane 109s, for ventilation of the cavity 104. Since the hose 108 is in fluid communication with the cavity 104, air may flow between the cavity 104 and the ambient environment through the air-permeable membrane 109. The air-permeable membrane 109 therefore allows equalisation of pressure between the cavity 104 inside the housing 102 and the ambient environment outside housing 102. The air-permeable membrane may comprise a non-woven porous membrane. The air-permeable membrane may comprise polytetrafluoroethylene. The air-permeable membrane may comprise a stretched porous polytetrafluoroethylene membrane. Providing the air-permeable membrane 109 on the hose 108 allows the air-permeable membrane 109 to be located at a position which is separated from the housing 102. As described above, the hose 108 may be configured such that when the battery unit assembly 100 is assembled in the vehicle 1000 the air-permeable membrane 109 is vertically above the housing 102. As shown in the embodiment in Figure 1, the housing 102 of the battery unit assembly 100 may be mounted under the floor of the vehicle 1000. As such, during a wading event the battery may be immersed in water. At the start of a wading event, the battery will be warm relative to the water. As the battery cools during wading, the pressure within the cavity 104 decreases. Ventilation of the cavity 104 is therefore needed during wading events to reduce risk of damage and water entering the housing. As shown in the embodiment in Figure 1, the hose 108 may be positioned in the vehicle 1000 such that the air-permeable membrane is above a maximum wading depth 1005 of the vehicle 1000. Therefore, the air-permeable membrane 109 will not be submerged during normal wading events. As such, the air-permeable membrane allows for the necessary ventilation of the cavity 104 during normal wading events whilst reducing the risk of ingress of water into the battery assembly unit 100 as the Water Entry Pressure of the membrane 109 will not be exceeded. The maximum wading depth 1005 is the maximum depth ofwater through which a vehicle is designed to travel. Beyond the maximum wading depth 1005 there is a risk that the vehicle engine and electronics may be damaged. The vehicle 1000 of the embodiment shown in Figure 1 is designed to have off-road capabilities. As such, the maximum wading depth 1005 of the vehicle may be at least 900 mm. Therefore, the hose 108 may positioned in the vehicle 1000 such that the air-permeable membrane 109 is at a height of at least 900 mm above the ground 1008 supporting the vehicle 1000. The height of the air-permeable membrane 109 above the ground may be in a direction perpendicular to the ground 1008. However, the invention is not limited to use with the vehicle shown in Figure 1. The battery unit assembly 100 may be used within a vehicle where the maximum wading depth 1005 may be at least 250 mm, 450 mm, 500 mm, 550 mm, 600 mm, 850 mm, 950 mm or 1000 mm. Therefore, the hose 108 may positioned in the vehicle 1000 such that the air-permeable membrane 109 is at a height of at least 250 mm, 450 mm, 500 mm, 550 mm, 600 mm, 850 mm, 950 mm or 1000 mm above the ground 1008 supporting the vehicle 1000. In certain embodiments, the air-permeable membrane 109 may be at a height of 100 mm or more above the maximum wading depth 1005 of a vehicle 1000. The air-permeable membrane 109 is for ventilation of the cavity 104 in a first operating range. The first operating range may correspond to pressure differences between the cavity 104 and the ambient environment experienced during normal use of the vehicle 1000 such as, for example, changes in altitude whilst driving, changes in the weather or ambient temperature and during wading events. The first operating range may comprise a difference in pressure of less than 150 mbar, or less than 100 mbar between the cavity 104 and the ambient environment. Therefore, the air-permeable membrane 109 permits ventilation for pressure equalisation between the cavity 104 and the ambient environment due to changes in altitude whilst driving, changes in the weather or ambient temperature, and water immersion of the housing 102 during wading. Rapid ventilation of the cavity 104 when the pressure difference between the cavity 104 and the ambient environment is greater than 150 mbarmay be provided by alternative means. The air-permeable membrane 109 may be selected to provide sufficient ventilation of the cavity 104 during the first operating range. The selection of the air-permeable membrane 109 may depend on the volume of air in the cavity 104 of the battery assembly unit 100. In particular, the size and air permeability of the membrane may be selected to provide sufficient ventilation of the cavity 104 during the first operating range. In the embodiments shown in Figures 1 to 5, to provide ventilation for the cavity 104, the battery assembly unit 100 comprises four air-permeable membranes 109 which each may have an air permeability of at least 500 cm3 / min, where the air permeation is measured at a differential pressure 1kPa. In certain embodiments, the air-permeable membrane of the hose 108 may be hydrophobic The hydrophobic property of the air-permeable membrane 109 may reduce the risk of water from, for example, rain or spray entering the battery unit assembly 100. However, in certain embodiments, the air-permeable membrane 109 may not be hydrophobic. Since the air-permeable membrane 109 may be positioned above the maximum wading depth of the vehicle 1000, the air-permeable membrane 109 will not be submerged during normal wading events in such embodiments. Therefore, the air-permeable membrane 109 may have a high air permeability and low water entry pressure. In a non-limiting example, the air-permeable membrane may have a water entry pressure of at least 60 kPa. The water entry pressure may be measured using the JIS L1092 B method (high water pressure). However, in alternative embodiments, the air-permeable membrane may have a water entry pressure that is lower than 60 kPa. The air-permeable membrane 109 on the hose 108 provides sufficient ventilation of the cavity 104 so that there is no need to provide additional air-permeable membrane 109s on the housing 102. As such, the housing 102 does not comprise an air-permeable membrane for ventilation in the first operating range. That is, there may be no air-permeable membrane fitted directly on the housing 102 for ventilation in the first operating range. Therefore, there may be no membrane for ventilation in the first operating range below the maximum wading depth of the vehicle 1000. As such, the risk of the water entering the housing 102 due, for example, to the Water Entry Pressure being exceeding during a wading event is further reduced. In certain embodiments, the housing 102 may not comprise an air-permeable membrane for ventilation of the cavity 104. That is, the housing 102 may comprise no air-permeable membrane for ventilation of the cavity 104 in the first operating range or any other operating range. That is, there may be no air-permeable membrane fitted directly on the housing 102. Thus, the risk of the water entering the housing 102 due to a water entry pressure of a membrane being exceeding during a wading event is removed. As shown in the embodiment in Figures 1 to 3, the distal end 112 of the hose 108 may comprise the air-permeable membrane. The distal end 112 of the hose 108 may comprise an end cap 122 that comprises the air-permeable membrane 109. An embodiment of the end cap 122 is shown in detail in Figure 4. In the nonlimiting embodiment in the Figure 4, the end cap 122 comprises a plurality of air permeable membranes. In the embodiment of Figure 4, the end cap 122 comprises four air-permeable membranes 109. However, the invention is not limited to this specific arrangement. In alternative embodiments, the end cap 122 may comprise one or more air permeable membranes. The end cap 122 may comprise one or more apertures 123 each covered by one air-permeable membrane 109. For example, in the non-limiting embodiment in the Figure 4, the end cap 122 comprises four apertures 123 each covered by one air-permeable membrane 109. Each aperture 123 may extend through the end cap 122 to fluidly connect an interior of the end cap 122 to the ambient environment. Therefore, air may pass between the interior of the end cap 122 and the ambient environment via the air-permeable membrane 109. As shown in the embodiment in Figure 4, the apertures 123 may be positioned on opposing sides of the end cap 122. In the embodiment of Figure 4, the end cap 122 comprises two apertures 123 in a first side of the end cap 122 and two apertures in an opposing second side of the end cap 122. As shown in the embodiment of the end cap 122 in Figure 4, each membrane may be provided within a ventilation structure 124. The ventilation structure 124 may comprise a plastic. The ventilation structure 124 may comprise a body portion (not shown) having an opening (not shown) extending therethrough. The opening may be covered by the air-permeable membrane 109. The air-permeable membrane 109 may be secured to the body portion by any suitable means. Non-limiting examples include welding the air-permeable membrane 109 to the body portion. The ventilation structure 124 may be connected to the end cap 122 by any suitable means. In certain embodiments, the ventilation structure 124 may comprise a thread (not shown) configured to engage a corresponding thread in an aperture 123 of the end cap 122. In an alternative embodiment, the ventilation structure 124 may form a snap fit with one of the plurality of apertures 123 in the end cap 122. In such embodiments, the ventilation structure 124 may comprise a plurality of legs (not shown) connected to the body. The legs may be configured to elastically deform. The legs may comprise a locking portion or projection (not shown) positioned at the end of each leg configured to secure the ventilation structure 124 to the hose 108. Once the legs have passed through the aperture 123, the locking portion may engage an inner surface of the hose 108 to prevent removal of the ventilation structure 124 from the end cap 122. The ventilation structure 124 may comprise a protective cover 126 arranged above the air-permeable membrane 109. The protective cover 126 may be spaced apart from the membrane so not as to inhibit air flow through the membrane. In certain embodiments, the battery unit assembly 100 may comprise a ventilation structure 124 as described in prior patent application US 2014 / 0283691 A1, which is incorporated herein by reference. However, the invention is not limited to this ventilation structure 124, and any suitable ventilation structure 124 may be used. Whilst Figure 4 shows one way by which air-permeable membranes 109 may be included in the end cap 122, the invention is not limited to the embodiment shown in Figure 4. The air-permeable membrane 109 or membranes may be attached to the end cap 122 in an alternative manner to the ventilation structure 124 shown in Figure 4. For example, the air-permeable membrane 109 or membranes may be attached directly to the hose 108. As shown in the embodiment in Figure 4, the end cap 122 may have a first end 128 and second end 130. The first end 128 ofthe end cap 122 may be closed. That is, the first end 128 of the end cap 122 may have a closed construction. The second end 130 ofthe end cap 122 may be connected to the tube body 118 ofthe hose 108. The end cap 122 may be connected to the tube body 118 by any suitable means. In certain embodiments, the second end ofthe end cap 122 may be configured to be received within the tube body 118. The second end ofthe end cap 122 may comprise a plurality of ridges 132 arranged to engage a corresponding set of ridges (not shown) within the tube body 118 to connect the end cap 122 to the tube body 118. The hose 108 may comprise a seal (not shown) arranged to provide a fluid tight seal between the tube body 118 and the end cap 122. The seal may comprise an o-ring. As shown in the embodiment in Figures 1 to 4, the hose 108 may comprise a curved portion 134 between the distal end 112 and proximal end 110. The curved portion 134 may be provided by one ofthe plurality of bends 114 in the hose 108. The curved portion 134 provides an air lock configured to restrict the flow of liquid from the distal end 112 to the proximal end 110 ofthe hose 108. The curved portion 134 is positioned between the air-permeable membrane 109 and the proximal end 110 ofthe hose. The curved portion 134 is configured so that the air-permeable membrane 109 is lowerthan the highest vertical point ofthe hose 108 when the battery until assembly 100 is within the vehicle 1000. Therefore, if liquid enters the distal end 112 ofthe hose 108 or through the air-permeable membrane 109 due to a failure, the water cannot flow under gravity to the proximal end 110 of the hose 108 due to the curved portion 134. As shown in Figure 3, when the battery unit assembly 100 is assembled within the vehicle 1000, the hose 108 extends vertically upwards from the proximal end 110 to the highest vertical point above the housing 102. The curved portion 134 ofthe hose 108 may coincide with the highest vertical point ofthe hose 108 above the housing 102. The curved portion 134 provides a bend 114 in the hose 108 which directs the hose 108 downwards from the highest vertical point so that the distal end 112 ofthe hose 108 is lowerthan the highest vertical point ofthe hose 108 above the housing 102. The distal end 112 ofthe hose 108 is therefore closer to the housing 102 than the curved portion 134 ofthe hose. Since the curved portion 134 is positioned between the air-permeable membrane 109 and the proximal end 110 ofthe hose, the air-permeable membrane 109 is closer to the housing 102 than the curved portion 134 ofthe hose. The curved portion 134, therefore, creates the air lock to restrict the flow of liquid from the distal end 112 ofthe hose 108 or the air permeable membrane into the housing 102. As shown in the embodiment of Figures 1 to 3, the battery unit assembly 100 may comprise a protective sleeve 136. The protective sleeve 136 may extend around at least a portion ofthe hose 108. The protective sleeve 136 may have a greater resistance to abrasion and / or impact resistance than the hose 108. In particular, protective sleeve 136 may have a greater resistance to abrasion and / or impact than the tube body 118 ofthe hose 108. For example, in non-limiting embodiments the protective sleeve 136 may comprise rubber orsilicon. The tube body 118 may comprise corrugated nylon. The protective sleeve 136 may be beneficial when the hose 108 is arranged to extend within the wheel arch 1002,1004 ofthe vehicle 1000 as shown in Figure 4 and a portion ofthe hose 108 may not be sufficiently covered by external trim in the wheel arch 1002, 1004. The protective sleeve 136 may therefore be positioned to cover this portion of the hose 108 to protect the hose 108 from abrasion and impacts from debris. The battery unit assembly 100 may comprise a plurality of fixings 138 for attaching the hose 108 to the vehicle 1000 or components of the vehicle 1000. Any suitable fixing 138 may be used to attach the hose 108 to the vehicle or components of the vehicle. As shown in the embodiment in Figures 1 to 4, each fixing 138 may comprise a clip configured to clip onto an exterior of the hose. A projection may extend away from the jaw. The projection may be attached to the vehicle 1000 or components in the vehicle 1000 to improve ease of attaching the hose 108. The projection may comprise a hole or slot to receive a fastener for attaching the fixing 138 to the vehicle. Alternatively, each fixing may comprise a cable tie extending circumferentially about the hose 108. The cable tie may comprise an end and a tie portion extending from the end. The end may comprise an aperture for receiving the tie portion. The end may comprise a projection. The projection may be attached to the vehicle 1000 or components in the vehicle 1000. The projection may comprise an aperture to facilitate attachment to the vehicle 1000 or components in the vehicle 1000. Figures 5 to 7 show another embodiment of a battery unit assembly 200. Reference numerals in Figures 5 to 7 correspond to those used in Figures 1 to 4 for like features but are increased by 100. The battery unit assembly 200 of the embodiment shown in Figures 5 and 6 is the same as the battery unit assembly 100 of the embodiment shown in Figures 1 to 4 except the shape of the hose 208. As described above, the vehicle 1000 of the embodiment shown in Figure 1 may be designed with off-road driving capabilities which affects the shape and length of the hose 108 in the embodiment shown in Figures 1 to 4. The battery unit assembly 200 of the embodiment shown in Figures 5 to 7 may be used in a vehicle 2000 which is not is designed for off-road driving. As such, the maximum wading depth of the vehicle may be lower. The maximum wading depth of the vehicle may be 250 mm or more. Therefore, the hose 208 may be shorter than the hose 108 of the embodiment shown in Figures 1 to 4. The distal end 212 of the hose 208 may be positioned adjacent to a side of a rear wheel arch 2004 rather than above the rear wheel arch 2004. Additionally, the hose 208 may take a different shape than the hose 108 of the embodiment shown in Figures 1 to 4 due to differing shape of the vehicle and components within the vehicle 2000. However, in the same manner as described for the embodiment of Figures 1 to 4, the hose 208 may comprise a plurality of bends 214. The hose 208 may comprise one or more straight 216 sections extending between or from the plurality of bends 214. The shape of each of the plurality of bends 214 and the length or the one or more straight sections 216 may differ from the embodiment of Figures 1 to 4 due to the different requirements of the vehicle 2000. In the same manner as described for the embodiment of Figures 1 to 4, the hose 108 comprises a curved portion 234 between the distal end 212 and proximal end 210 to provide an air lock configured to restrict the flow of liquid from the distal end 212 to the proximal end 210 of the hose 208. As shown in Figure 5, the curved portion 234 may be positioned between the air-permeable membrane 109 in the end cap 222 and the proximal end 210 of the hose 208. In the embodiment shown in Figures 5 to 8, the fixings 238 differ to the fixings 138 described above for the embodiment in Figures 1 to 4. In the embodiment in Figures 5 to 8, each fixing 238 comprises a cable tie extending circumferentially about the hose 208. The cable tie may comprise an end and a tie portion extending from the end. The end may comprise an aperture for receiving the tie portion. The end may comprise a projection. The projection may be attached to the vehicle 2000 or components in the vehicle 2000. The projection may comprise an aperture 239 to facilitate attachment to the vehicle 2000 or components in the vehicle 2000. However, the battery unit assembly 200 is not limited to the fixings 238 shown in Figures 5 to 8. Any suitable fixing may be used. In certain embodiments, the fixings 238 may be the same as the fixings 138 described above for the embodiment shown in Figures 1 to 4. In the embodiment shown in Figures 5 to 8, whilst not shown, the battery unit assembly 200 may comprise a protective sleeve. In either of the above-described embodiments, the housing may comprise an exhaust mechanism for ventilation of the cavity in a second operating range. The second operating range may comprise a difference in pressure of greater than 150 mbar between the cavity and the ambient environment. Therefore, the second operating range may require rapid ventilation of the cavity which is not possible through the air-permeable membrane on the hose. By providing the exhaust mechanism on the housing the speed at which pressure can be released from the cavity is increased. The exhaust mechanism may not comprise an air-permeable membrane further increasing the speed at which pressure can be released from the cavity and, also, reducing the risk of water entering the cavity 104 during a wading event. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. In the embodiment shown in Figure 4, air-permeable membranes 109 are provided on opposing sides of the end cap 122. However, the invention is not limited to this arrangement. In alternative embodiments, the air-permeable membranes 109 may all be on the same side of the end cap or each air-permeable membrane 109 may be on a different side of the end cap. In an alternative embodiment, the end cap may comprise one or more air permeable membranes on the first end of the end cap. In the embodiments shown in the Figures, the distal end of each hose is positioned near the rear wheel arch. However, the invention is not limited to this arrangement. The distal end of each hose may be positioned in an alternative location above the housing within the vehicle.

Claims

1. A battery unit assembly comprising:a housing defining a cavity for enclosing a battery; anda hose connected to the housing and in fluid communication with the cavity;wherein the hose comprises an air-permeable membrane for ventilation of the cavity in a first operating range; andwherein the housing does not comprise an air-permeable membrane for ventilation of the cavity in the first operating range.

2. The assembly according to claim 1, wherein the housing does not comprise an air-permeable membrane for ventilation of the cavity.3, The assembly according to any one of the preceding claims, wherein the air-permeable membrane of the hose is hydrophobic.

4. The assembly according to any one of the preceding claims, wherein the hose comprises a proximal end connected to the housing and a distal end; wherein the distal end comprises the air-permeable membrane.

5. The assembly according to claim 4, wherein the hose comprises a curved portion between to the distal end and the proximal end, wherein the curved portion provides an air lock configured to restrict the flow of liquid from the distal end to the proximal end of the hose.

6. The assembly according to any one of the preceding claims, comprising a protective sleeve extending around at least a portion of the hose.

7. The assembly according to any one of the preceding claims, wherein the hose comprises a tube bodyand an end cap connected to the tube body, the end cap comprising the air-permeable membrane.

8. The assembly according to any one of the preceding claims, comprising the battery.

9. The assembly according to any one of the preceding claims, wherein the first operating range comprises a difference in pressure of less than 150 mbar between the cavity and the ambient environment.

10. The assembly according to any one of the preceding claims, wherein the first operating range comprises a difference in pressure of less than 100 mbar in pressure between the cavity and the ambient environment.

11. A vehicle comprising a battery unit assembly according to any one of the preceding claims, wherein the hose is positioned in the vehicle such that the air-permeable membrane is above a maximum wading depth of the vehicle.5 12. A vehicle according to claim 11, wherein the maximum wading depth is at least 250 mm.

13. A vehicle according to claim 11, wherein the maximum wading depth is at least 900 mm.

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